<template>
  <div class="pagination"> 
    <button :disabled="pageNo<=1" @click="$emit('changePageNo',pageNo-1)">上一页</button>
    <button v-show="continueStartEnd.start>1" @click="$emit('changePageNo',1)">1</button>

    <button  v-show="continueStartEnd.start>2">···</button>

    <button v-for="page in continueStartEnd.end" 
    @click="$emit('changePageNo',page)"
      :class="{ active: page === pageNo }"
    v-if="page >=continueStartEnd.start">{{ page }}</button>

    <button v-show="continueStartEnd.end<totalPages-1">···</button>
    <button v-show="continueStartEnd.end<totalPages" @click="$emit('changePageNo',totalPages)">{{totalPages}}</button>
    <button :disabled="pageNo===totalPages" @click="$emit('changePageNo',pageNo+1)">下一页</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: ["totalPages", "continuePage", "pageNo"],
  computed: {
    continueStartEnd() {
      const { totalPages, continuePage, pageNo } = this;
      let start = 0,
        end = 0;
      if (totalPages < continuePage) {
        start = 1;
        end = totalPages;
      } else {
        start = pageNo - Math.floor(continuePage / 2);
        end = pageNo + Math.floor(continuePage / 2);
        if (start < 1) {
          start = 1;
          end = continuePage;
        }
        if (end > totalPages) {
          end = totalPages;
          start = totalPages - continuePage +1;
        }
      }
      console.log(start, end);
      return {
        start,
        end,
      };
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>
